DESCRIPTION: Contact with semen is the major mechanism for sexual transmission of HIV but there is little information on biological and cellular factors determining the rate, timing or levels of HIV in semen. The long-term goals of this research project are: to test the hypothesis that the HIV virus load in semen is highly variable over the course of infection and is influenced by both systemic and local urogenital factors; and develop strategies to reduce HIV transmission by lowering the virus load in semen. The three specific aims are to correlate shedding of HIV with host factors, cellular response in semen, and shedding of cytomegalovirus (CMV) in semen. The investigators will test the hypothesis that the male reproductive tract is distinct from the systemic compartment. The plan is to measure levels of HIV in semen and determine if shedding is more likely among men with advanced clinical stage of infection, genitourinary tract signs and symptoms, reduced cellular immune status in peripheral blood or those who are not on antiretroviral therapy. Regarding the cellular response in semen, the investigators plan to test the hypothesis that the local cellular response in semen limits shedding of HIV. Specifically, they will measure CD4, CD8 and polymorphonuclear cell counts and percentages in semen.Findings will be compared with titers of HIV viral forms and with isolation of virus in culture to determine if men with higher cell counts in their semen have lower titers of HIV. And finally, the investigators will test the hypothesis that shedding of CMV in semen enhances shedding of HIV. They will measure HIV and CMV titers in semen using polymerase chain reaction (PCR) and infectious virus using culture systems. The goal is to determine if shedding of CMV enhances the likelihood or titers of HIV in semen. The localization of HIV and CMV in semen fractions will also be compared.